Irrigation systems for domestic crops, residential landscapes, commercial landscapes, municipal landscapes and nurseries, etc. often utilize an electronic irrigation controller such as is disclosed in U.S. Pat. Nos. 4,165,532, and 4,827,155. Such electronic controllers are programmable, and are able to store a variety of irrigation programs. Programming of irrigation schedules is facilitated at the electronic controller by means of an alpha-numeric display and key pad or similar where information required for creating simple, temporal based irrigation schedules such as day of week, time of day, station number or valve number, run time or irrigation duration etc. may be input and reviewed. Such electronic controllers are typically wired to a plurality of electronic valves located throughout the irrigation system. During normal operation of the automatic irrigation system, the electronic irrigation controller proceeds by opening and closing the electronic irrigation valves as per the temporal parameters present in irrigation schedule(s) that have been programmed into the irrigation controller by the user. Typically, water under constant pressure is supplied by municipalities or water purveyors such that the opening of single or multiple electronic valves present in the irrigation system by the irrigation controller allows water to flow through particular zones or stations of the irrigation system such that water will be delivered on to the area to be irrigated until the closing of the electronic valves by the electronic controller as per the irrigation program.
Temporal based electronic irrigation system controllers have been available for decades and have had wide market acceptance because they have allowed homeowners, managers of commercial landscapes, and nurseries, etc. to irrigate landscapes and plant materials automatically and regularly on a temporally based schedule which has been input and stored in the electronic irrigation controller.
Over the years, however, an ever expanding population and increased urbanization has resulted in a proportional increase in residential and commercial landscaping square footage, which in turn has resulted in an increase in outdoor irrigation water consumption. Many regions throughout the U.S. now face water shortages and have therefore been forced to scrutinize high water use practices such as landscape irrigation, and to also examine opportunities for reducing water consumption, and in particular, to reduce water usage in high water consumption practices such as landscape irrigation.
In September of 2002, The United States Environmental Protection Agency published a report entitled “Water Efficient Landscaping” which stated that: “according to the US Geological Survey, of the 26 billion gallons of water consumed daily in the United States, approximately 7.8 billion gallons, or 30% is devoted to outdoor uses. The majority of this is used for landscape irrigation.”
While the advent of electronic irrigation controllers has enabled irrigation of landscapes and plant materials to be performed automatically and on a regular schedule, these controllers have also been criticized for their lack of ability to automatically adjust irrigation schedules as a function of seasonal changes and local weather conditions such that irrigation is reduced and water is conserved when, for example, cooler or more humid weather, or even rain reduces landscape irrigation requirements. The essence of this criticism is that an electronic irrigation controller which has been programmed to deliver any volume of water above and beyond the minimum amount required for plant material sustainability may be considered to be wasteful of water resources.
In 1881, the State of California and cooperative agencies began using evaporation pan data to help estimate crop water use for purposes of water conservation. By recording the direct evaporation of water from a metal pan of known size, located in a prescribed environment, an estimation of crop water requirements would be made and thereby provide water planners and others with an effective tool for projecting water use for specific crops. This is an early example of weather based irrigation control. Since that time, many different formulas for estimating crop or landscape water usage have been put forth by the scientific community, each with varying levels of complexity and sophistication. Although there are many different such formulas in use today, the objective of each calculation method is essentially the same in that one to several physical and/or weather based factors such as, but not limited to extraterrestrial solar radiation, net solar radiation, mean ambient temperature, wind speed, and plant material water demand are used to estimate the amount of water lost at a particular location due to a combination of ground evaporation and natural plant material transpiration.
For a given area, water lost through ground evaporation and natural plant material transpiration has come to commonly be known as Evapo-Transpiration, or ET; and the variety of associated formulas for calculating ET have come to be known as ET calculations, ET formulas, or ET equations. ET calculations result in an integer value with units of inches or millimeters of water per unit time, such as inches or millimeters of water per day.
The introduction of so called Weather Based Irrigation Controllers (WBICs), or Smart Controllers, such as are disclosed in U.S. Pat. Nos. 4,962,522; 5,097,861; 5,208,855; 5,479,339; 5,696,671; 6,298,285 and 6,314,340 respond to the criticisms placed on simple temporal based irrigation controllers by utilizing various methods of estimating water losses due to ET, and then automatically adjusting irrigation programs such that subsequent irrigation cycles will replenish the lost water. Thus, many WBICs are often referred to as Evapo-Transpiration controllers, or ET controllers. The methods utilized by ET controllers for determining weather based watering schedules include the utilization of historical ET data for a given location, area or zone; and/or publicly available real-time ET data for a given location, area or zone; and/or the utilization of local auxiliary sensors and weather stations for obtaining local data required to calculate local ET values for a given location, area, or zone; and/or the utilization of latitudinal location such that ET values may be interpolated for a given location, area, or zone. The previously cited list of methods in which WBICs may obtain and/or generate and then utilize ET data is not meant to be comprehensive, but to demonstrate the wide variety of methods which are currently in use. Furthermore, it should be appreciated that while many different methods exist for obtaining, generating and utilizing ET data, WBIC controllers generally utilize the different methods with the same target objective which is to automatically and continuously alter programmed irrigation schedules based on weather conditions such that a theoretically adequate amount of water is delivered by the irrigation system to replenish water lost due to ET and thus satisfy landscape requirements without over watering.
Additionally, there is WBIC technology such as is disclosed in U.S. patent application Ser. No. 11/879,700 that distinguishes the utilization of certain weather based data, specifically extraterrestrial radiation, or RA, as separate from the set of weather data used in ET calculations. This WBIC technology requires that the WBIC's physical location be entered in to and stored by the WBIC so that an average summer high temperature for the WBIC's physical location may be obtained by the WBIC from a set of historical geo-environmental data for the entire U.S. which is stored by the WBIC's non-volatile memory. The zip code of the WBIC's physical location may be entered into the WBIC's user interface; or alternatively, the WBIC may be outfitted with a GPS system so that the WBIC can automatically obtain its physical location from global positioning satellites. This particular WBIC technology also requires that current local ambient temperature readings be obtained by an auxiliary external temperature sensor so that current ambient temperature readings at the WBIC's physical location may be taken together with stored historical high temperature data corresponding to the WBIC's physical location such that a standard temperature budget factor may be calculated and used to automatically alter irrigation programs accordingly. While this particular WBIC technology differs from ET controllers in that it does not attempt to replenish water lost do to evapo-transpiration, it is quite similar to ET controllers in its necessity to have its physical location entered in to the unit, its need to store historical geo-environmental data for the entire U.S. in look-up tables, its requirement to utilize local weather data obtained by an auxiliary temperature sensor, and in its requirement to perform mathematical calculations with externally obtained sensor data together with stored historical weather data in order to generate weather based irrigation programs. These similarities to ET controllers are cited to demonstrate this WBIC technology's comparable complexity and subsequent cost to that of ET controllers.
Unfortunately, and despite the many years that WBICs have been commercially available, WBICs have gained little market penetration despite aggressive rebate incentive programs offered to homeowners by municipalities and water purveyors whereby as much as 100% of the cost of WBICs is rebated to the homeowner, and/or the homeowner is required to trade in their existing temporal based irrigation controllers for new WBICs. There are a number of factors which may account for the low market penetration of WBICs including WBIC price, complexity and performance.
Due to the amount of weather data that must be obtained and/or generated by WBICs, they are by nature complex pieces of equipment. As previously stated, many WBICs require the use of auxiliary sensor input from various types of weather sensors or weather stations so that mathematical calculations may be performed by the WBIC resulting in the generation of weather based irrigation programs. If no additional installation cost is to be incurred, the homeowner must not only attach the WBIC to his or her existing irrigation system, but may also have to select a location on his or her property for weather sensor or weather station installation which will be representative of the weather conditions experienced by the entire landscape. For those homeowners not skilled in the installation of weather sensors or weather stations, this requirement can be quite challenging and prone to errors resulting in improper operation of the WBIC.
After WBIC installation is complete, the initial set up and programming of WBICs requires the input of WBIC physical location as well as many variables that are characteristic of the landscape environment present at each different watering zone or station to be irrigated by each separate electronic irrigation system valve controlled by the WBIC such as soil type, physical slope gradient, percent sun exposure, root zone working storage depth, identification of landscape plant material types, crop or landscape coefficient, water delivery method (spray, bubbler, drip, rotator, etc.), and irrigation system precipitation rate. If the homeowner determines that the installation and initial set up of the WBIC is beyond his or her landscaping and horticulture expertise and thus too complex, installation and initial set up of the WBIC will require the hiring of an irrigation or landscape professional which results in additional cost to the homeowner.
Another factor which may help account for the low market penetration rate of WBICs is the documented low water savings obtained through the use of WBICs. A report entitled “Evaluation of Weather Based “Smart” Irrigation Controller Programs” which was prepared for the California Department of Water Resources by The Metropolitan Water District of Southern California and The East Bay Municipal Utility District on Jul. 1, 2009 presented the results of the impact of 3,112 WBICs installed at 2,294 sites within the State of California. These sites met the fundamental data requirements established for inclusion in this study, i.e. one full year of pre- and post-installation water usage billing data, corresponding climate data, a measurement of the landscape area at the site, and basic information about the site, controller, and installation. This report states that “Overall, outdoor water use was reduced by an average of 47.3 kgal per site (6.1% of average outdoor use) across the 2,294 sites examined in this study as part of the California Weather-Based Irrigation Controller Programs. This reduction was found to be statistically significant at the 95% confidence level.” The characteristic high cost and complexity of WBICs, coupled with the ability to deliver only 6.1% average water savings, may mean that the typical homeowner is unlikely to be motivated to discard their existing, perfectly good irrigation controller and replace it with a WBIC. Perhaps more importantly, at only 6.1% average water savings, the overall water conservation performance provided by WBICs does not provide municipalities and water purveyors with the amount of water savings they require.
Another interesting finding cited in the “Evaluation of Weather Based “Smart” Irrigation Controller Programs” report states that “While the overall impact of smart controllers is expected to reduce irrigation demands, irrigators who historically apply less than the theoretical irrigation requirement for their landscape, can expect their water use to increase after installing a smart controller. On the individual site level, a total of 56.7% of the 2,294 study sites had a statistically significant reduction in weather-normalized application ratio, while 41.8% of sites had a statistically significant increase in application ratio. For 1.5% of sites, there was not a statistically significant change in application ratio.”
Surprisingly, 41.8% of these 2,294 WBIC study sites experienced an increase in water usage. WBIC manufacturers have stated that the true performance of WBIC technology should be evaluated based on the WBIC's ability to deliver adequate landscape irrigation as determined by prevailing weather conditions, and not as to whether or not the WBIC irrigates more or less than the pre-WBIC irrigation controller. Were these 41.8% of study participants practicing deficit irrigation techniques, or purposely, or unknowingly stressing their landscape plant materials prior to installation of the WBIC; or is it that, as compared to humans, even state of the art WBIC technology lacks the capability to more precisely and cost effectively address the myriad of factors and requirements for determining adequate yet conservative landscape irrigation. While not directly addressed in the report, one reasonable conclusion would be that a significant number of irrigators (homeowners) in the general population may be better able to determine conservative yet adequate irrigation programs than today's state of the art WBIC technology. Yet another reasonable conclusion would be that state of the art irrigation controller technology is misguided in its attempt to completely eliminate human participation in determining conservative yet adequate landscape irrigation practices. This conclusion is supported by a recent article published in “Lawn and Landscape” magazine in November, 2009 which, in response to a recent Texas A&M WBIC study whose results concluded that WBICs used more water than required by the university's test landscapes, states that “Many of the studies undertaken so far on smart controllers have shown that without proper programming and follow up to adjust the program, the controller will not save much—if any—water. These same studies show that when the follow-up adjustments are performed, the controllers reduce water use considerably.” Thus it can be seen that despite the continued effort to eliminate the human from the landscape irrigation process, it appears that even state of the art irrigation controller technology continues to require human intervention in order to reap the expected benefits.
While it may be possible to improve upon existing WBICs by adding still more technology and sophistication in efforts to completely eliminate human participation in the landscape irrigation process, autonomously and automatically generate adequate irrigation programs, and produce the water savings expected by municipalities and water purveyors, these advancements will most likely be accompanied by an increase in cost and complexity. What follows is a discussion of alternatives.
As previously mentioned, a common criticism of simple temporal based irrigation controllers is their lack of ability to automatically adjust irrigation programs as a function of seasonal change and to match local weather conditions. The Metropolitan Water District of Southern California's website posts data (FIG. 1) demonstrating the amount of water which could be conserved if electronic irrigation controllers were adjusted to match local weather conditions “instead of just twice a year, which is typical for many people.” The amount that may be saved is estimated to be as much as 40%.
In recent years and in an effort to simplify the articulation, communication and implementation of weather based irrigation practices for the general population, an irrigation or watering factor, sometimes called a watering index, has been adopted by many water purveyors throughout the U.S. One far reaching advantage of a watering index approach to outdoor water conservation is its ability to be implemented using the large installed base of existing electronic irrigation controllers, independent of irrigation controller type or technology. Thus, a watering index approach may be applied more broadly, more rapidly, more cost effectively, and with less effort than mass or even gradual implementation of new WBIC technology.
The watering index principle was developed by Mr. John Wynn of the State of California Department of Water Resources, and while there are variations on how a watering index may be calculated, it is generally taken to be a ratio of current local ET to the ten year historical ET high for a given location. In another variation, historical weekly and monthly averages may also be used to calculate weekly and monthly watering index estimates and forecasts (FIG. 2). A noteworthy tenet of the watering index principle is that a watering index value is not expressed in terms of inches or millimeters of water per unit time, in fact, a watering index has no units at all, it is simply a percentage. This is because the watering index principle assumes that the grower, professional landscaper or homeowner, through experience and interaction, is already aware of the many factors present in his or her area to be irrigated which determine adequate irrigation and is therefore able to program their irrigation controller with adequate yet conservative watering durations for each zone having already taken the many influential factors into account. A watering index is intended to aid growers, landscapers and homeowners in adjusting watering schedules to better match the variable factors of local weather conditions and seasonal change as a percentage or fraction of their self determined maximum adequate yet conservative watering requirements during the hottest, driest time of year. For example, in the Northern hemisphere, a watering index is typically at or near 100% during July and August, and is only a fraction of this during the remaining months of the year.
Retail water agencies that have adopted a watering index as a method for outdoor water conservation will typically publish weekly or monthly watering index values on their websites. Once obtained from the local water district, irrigation programs for irrigation systems utilizing a watering index approach and served by the local water district may be safely adjusted to the prescribed watering index value. It should again be pointed out that a watering index does not specify the durations of irrigation schedules, or volumes of water that should be replenished. Instead, a watering index simply specifies a value which is a fraction or percentage of the reference 100%, as self determined by the irrigator, which occurs during the warmest, driest time of year.
FIG. 1 shows a typical ET curve and the step-curve created from watering index values. Similar to ET, watering indexes are highest during the warmest periods of the year, and lowest during the coolest periods of the year. The third curve (also a step curve) shows the water used when the irrigation program is adjusted just twice a year—a typical irrigation control method for many homeowners and landscapers. The blue area present between the step curves represents the amount of water, which is conserved when irrigation schedules are based on weekly watering index values as opposed to a typical bi-annual adjustment.
FIG. 2 shows a calendar with a water purveyor's recommended monthly watering index values which have been forecast for the entire year.
Non-WBIC electronic irrigation controllers equipped with a built in watering index percentage adjustment feature which allow irrigators to perform a global adjustment of their irrigation programs by turning a dial to the desired watering index percentage value have been commercially available for several years. This feature allows global adjustment of the irrigation program for each irrigation system zone simultaneously. A fault remains, however, in that because the aforementioned watering index percentage adjust feature is integrated into the controller, in most circumstances this feature along with the controller will be installed outdoors in locations not frequently seen or visited by the irrigator. Because electronic irrigation controllers, including those with watering index percentage adjust features, are typically and intentionally installed outdoors, out of plain sight and out of mind, even these controllers, in many cases, are not adjusted as frequently as intended due to inconvenience. Furthermore and despite the many advantages of watering index implementation, an additional practical problem exists for water purveyors seeking aggregate water savings in that the vast majority of homeowners and landscapers have older irrigation controllers which do not have an integrated watering index adjustment feature. While these homeowners and landscapers may wish to respect and implement a watering index principle as put forth by their local water district, they may find it too challenging and/or inconvenient to frequently calculate new watering index based irrigation programs each day, week or month, and then re-program their irrigation controllers to correspond with the desired watering index value. In fact, many older irrigation controllers can only be adjusted in 5-minute increments making it impossible to adjust irrigation programs based on a watering index value. The result is that the vast majority of homeowners and landscapers, regardless of electronic controller make, model, or vintage, are likely to default to the bi-annual controller adjustment method depicted in FIG. 1 which, in aggregate, represents a significant amount of wasted water for retail water agencies.
Thus it can be seen that typical irrigation controllers, WBIC or non-WBIC, are at best, inconvenient to adjust, and at worst, too challenging to adjust; that this inconvenience and/or difficulty leads to an unacceptable infrequency of controller adjustment; and that infrequency of controller adjustment results in over watering and therefore wasted water resources.
In summary, it follows then that an improved approach to conserving water during landscape irrigation practice would be to build upon the many municipal and university studies which have observed several thousands of WBICs in varying regions of the U.S. and demonstrate, directly or indirectly, that the inclusion of human participation in the landscape irrigation process is either required or is at least beneficial in reducing the amount of water that is unnecessarily wasted in landscape irrigation. Rather than the elimination of human participation in landscape irrigation through complex and expensive technology, a simpler, less costly and more effective approach would be to embrace and further engage human participation in the landscape irrigation process. Additionally, it follows that, due to its ability to be immediately implemented across the large installed base of existing irrigation controllers independent of controller type or technology, a watering index based approach is advantageous because it will more rapidly, more cost effectively and with minimum effort result in broad based aggregate water savings for water purveyors. Furthermore, it follows that by addressing the practical issues of convenience and ease with which a watering index based approach may be implemented, achieving the broad based aggregate water savings desired by municipalities and water purveyors may be enabled.
A simpler and more cost effective improvement over WBICs which addresses the large installed base of existing electronic irrigation controllers as well as future generations of new, low cost temporal based irrigation controllers for the purpose of reducing waste and conserving water used in landscape irrigation is addressed in this disclosure.